The invention relates to a drive device of the type used for tiltable and/or sliding covers, such as for a motor vehicle roof. Prior art covers have been movable by a drive actuated by a crank, the crank being connected to a shaft provided with a gear, said gear meshing with a drive pinion for the sliding mechanism of the cover in a driving relationship, or even constituting the drive pinion itself, whereby a niche is provided in the headlining, into which niche the crank can be folded in a certain position.
If the crank is connected rigidly with the cover by the drive, the crank will be in a position in which it can be folded into the niche only in a few positions of the cover. This circumstance is insignificant as far as normal sliding roofs are concerned, since half a turn of the crank, the maximum amount necessary to bring the crank arm into the folding position, does not result in very much displacement of the cover, so that the user can easily bring the sliding roof into a position in which the crank arm can be folded into the niche. In the case of tiltable covers, on the other hand, the problem arises that only a few, for example two, turns of the crank are provided for tilting the cover, so that the crank can be folded into the niche in only a few drive positions of the cover, and turning the crank through a half revolution, the maximum amount necessary to bring the crank into a folding position, results in a considerable change in the position of the cover. It would be desirable, however, if the crank could be folded away in the largest number of possible positions of the cover, preferably with the cover in any position. To achieve this goal, it has already been proposed (German Offenlegungsschrift No. 24 26 765 which corresponds to U.S. Pat. No. 3,976,325) to provide a releasable coupling between the hub of the crank and the drive pinion, so that the crank can be separated at any time from the drive mechanism, with the cover in any position, and turned so that it can be folded into the concave niche. However, a coupling of this kind is relatively costly and requires special actuation by the user, which is undesirable since his attention is distracted from the rod.
Additionally, it has been proposed, in commonly assigned co-pending Ser. No. 863,709, filed Dec. 23, 1977, U.S. Pat. No. 4,113,304 which is a continuation of U.S. patent application Ser. No. 772,675, filed Feb. 28, 1977 now abandoned, to mount a gear of a drive mechanism loosely on a shaft and provide a drive plate to rotate the gear by means of the shaft in both rotational directions, said drive plate being provided with a stop which cooperates with a stop on the gear. In this arrangement, play is provided between the shaft and the driving plate corresponding to the annular range determined by the circumferentially measured sum of the lengths of the stops. While the arrangement of Ser. No. 772,675 is an improvement over that of U.S. Pat. No. 3,976,325, the present invention is intended as a further improvement thereover.
Hence, a goal of the invention is to allow the crank to be folded away into the niche with the cover in any position, by simple means and without the requirement of special actuation.
This goal is achieved according to the invention by virtue of the fact that a free-running device (i.e. a freely traveling member such as a ball or roller bearing) is disposed between the crank and the shaft or between the shaft and the gear, allowing the crank to turn freely through 360.degree..
The proposal according to the invention makes it possible to turn the crank backward with the cover in any position (because of the free-running device) into a position in which it can be folded into the niche. No manually actuatable coupling is provided in the proposal according to the invention, so that the user can bring the crank into a folding position without having to turn his attention from the road.
An especially simple free-running device is achieved when a helical groove is provided in one of the parts to be coupled together and a straight groove is provided in the other one of the parts to be coupled, said straight groove running parallel to the lengthwise central axis of the helical groove and delimiting a receiving space for a locking ball with said helical groove, whereby the length of the straight groove corresponds to the pitch of the helix. When the cover is actuated, the locking ball is located at one end of the straight groove. If the crank is to be brought into a folding position with the cover in any position, the crank can be turned backward without driving the drive pinion, since the locking ball is displaced in the straight groove by the helical groove.
Preferably, the helical groove is located in the wall of the hole in the gear which accepts the shaft and the straight groove is located in the outside surface of the shaft.
In order to prevent the tilted cover from being moved out of position because of the free-running device by external influences, for example wind pressure, it is advantageous to provide a locking device which locks the free-running device when the crank is folded away, preventing the gear from turning. This locking device can be formed by a lengthwise displaceable pin, said pin being disposed in the crank hub mounted on the shaft and fitting into one of a plurality of depressions disposed along an arc in the underside of the gear when the crank is folded away. Alternatively, instead of a locking device of the type described above, spring means may be provided which tend to hold the cover in a tilted position, and hence to counteract the wind pressure which acts upon the cover as the vehicle moves.
These and other objects, features and advantages of the present invention will become more apparent from the following description when taken in connection with the accompanying drawings which show, for purposes of illustration only, preferred embodiments accordance with the present invention.